Electrical switch having contacts provided with rollers

ABSTRACT

A knife-type electrical switch including a blade contact and a pair of roller contacts between which the blade contact moves when the switch closes. The rollers are rotatable about axes substantially perpendicular to the direction of blade movement between them. The rollers have tapered ends, and the blade edge facing the rollers diverges from the rollers. Each roller is carried by an arm mounted to pivot about a point spaced from the rollers, and spring means constantly urge the arms and hence the rollers toward each other.

D United States Patent [151 3,648,003 Wiktor 51 Mar. 7, 1972 [54]ELECTRICAL SWITCH HAVING CONTACTS PROVIDED WITH 1,740,640 12/1929 Austin..200/166 BB ROLLERS 1,891,935 12/1932 Lapsley..... ..200/166 BB [72]Inventor: Dominik M. Wiktor, Ctanford, NJ. Primary Examiner-H. 0. Jones[73] Assignee: Automatic Switch Company mmmeyfBreltenfeld Levme [22]Filed: Jan. 29, 1971 [57] ABSTRACT [21] Appl. No.: 111,064 A knife-typeelectrical switch including a blade contact and a pair of rollercontacts between which the blade contact moves when the switch closes.The rollers are rotatable about axes 'g "200/166 efi substantiallyperpendicular to the direction of blade movement between them. Therollers have tapered ends, and the [58] Field of Search ..200/166 BB,166 E, 162 blade edge facing the toners diverges from the [ones Each[56] References Cited roller is carried by an arm mounted to pivot abouta point spaced from the rollers, and spring means constantly urge theNIT STATES PATENTS arms and hence the rollers toward each other.

l,666,978 I 4/1928 Sachs ..200/ 166 BB 7 Claims, 5 Drawing FiguresPatented March 7, 1972 2 Sheets-Sheet 1 FIG.

INVENTOR OOMM/IA M. ll/(7'02 ATTORNEYS FIG. 2

Patented March 7, 1972 3,648,003

2 Sheets-Sheet 2 M/M/Al/K M W/KTUZ MORNEYS ELECTRICAL SWITCH HAVINGCONTACTS PROVIDED WITII ROLLERS This invention relates to electricalswitches, and more particularly such a switch adapted to close when, atthe instant of closure, a high current flows in the circuit beingcompleted by the switch.

When a switch closes to complete an electrical circuit, the currentflowing through the switch contacts and the parts which support themproduces a magnetic repulsive force tending to separate the contacts.The magnitude of this repulsive force is a function of the current valueinvolved, and hence high currents produce very large repulsive forces.

Certain types of switching devices, such as safety switches, contactors,circuit breakers, and interrupters, must be designed to close not onlywhen normal current flow is present, but also on occasion when anabnormally high current is flowing, such as happens when the circuit isheavily overloaded, or when a fault current, such as a high in-rushcurrent or short circuit current, is present. On such occasions themagnetic repulsive force tending to separate the contacts as they closeis very large, and hence the mechanism associated with the switch mustbe made powerful enough to overcome the repulsive force and insure thatthe switch closes and remains closed.

Switching devices of the type mentioned above most commonly employbutt-type contacts which are especially susceptible to the repulsiveforce mentioned above, and which furthermore have a tendency to bounceand separate when they make contact. Therefore, the switch closingmechanism must be designed to overcome both this bounce and the highestrepulsive force the switch is likely to encounter. Some switches employknife-type contacts in which a blade moves between two contact fingersspring biased toward each other so to tightly squeeze the blade betweenthem. Knife-type contacts, although they bounce less on closing, dopresent a frictional drag between the closing contacts which must beovercome by the closing mechanism of the switch.

It will be appreciated therefore that switch closing mechanisms must bedesigned with a large amount of available energy even though all thisenergy may be needed only on occasion. This over design" is not onlycostly, but it also introduces excessive wear on all associated parts ofthe switch, since the full available energy of the closing mechanism isused to close the switch each time it operates, whether or not anabnormally large repulsive force is present. It is difficult to reducethat portion of the closing mechanism energy needed to overcome therepulsive force since the force occurs inherently as a result of thecurrent flowing through the switch.

However, it is an object of the present invention to reduce that portionof the closing mechanism energy needed to overcome the reaction of theswitch contacts when they engage each other.

It is another object of the invention to provide a switch havingknife-type contacts which are subject to greatly reduced frictional dragwhen they close, as a result of which the available energy of the switchclosing mechanism can be reduced.

It is another object of the invention to provide contacts having alarger than usual effective contact surface, whereby the useful life ofthe contacts is extended.

It is a further object to provide such a switch wherein the contacts arespecially shaped to effect more rapid quenching of the arc when theswitch opens.

Additional objects and features of the invention will be apparent fromthe following description in which reference is made to the accompanyingdrawings. In the drawings:

FIG. 1 is a side elevational view of the contact assembly portion of aswitch according to the present invention, the contacts being shownclosed in solid lines and open in broken lines;

FIG. 2 is a top view of the contact assembly;

FIG. 3 is a front elevational view of the contact assembly, partially incross section, taken along the line 33 of FIG. 1;

FIG. 4 is a fragmentary cross-sectional view of the primary arcingcontacts at the instant of contact between them; and

FIG. 5 is a fragmentary side elevational view of the primary arcingcontacts immediately after opening.

The switch contact assembly chosen to illustrate the present inventionincludes a base 10 and a shaft I1 pivotable with respect to the base.Base 10 carries three stationary contacts, namely, a main contact, andprimary and secondary arcing contacts. Shaft 11 carries three movablecontacts, namely, a main contact, and primary and secondary arcingcontacts.

Shaft 11 has a square cross-sectional shape, and mounted on the shaftfor rotation with it is a rigid channel-shaped contact arm 12, itscross-sectional shape being best seen in FIG. 3. At one end, contact arm12 has a depression 13 for accommodating two adjacent sides of shaft 11,and a bracket 14 is furnished having a similar depression for.accommodating the other two adjacent side of shaft 11. Four screws 15interconnect the end of contact arm 12 with bracket 14 to fix thecontact arm to shaft 11. Contact arm 12 carries all three movablecontacts of the switch, and the switch includes conventional mechanism(not shown) for rotating shaft 11 to produce movement of the movablecontacts for closing and opening of the switch.

Arranged below contact arm 12 is the movable main contact 19. Fourexternally threaded studs 20 project upwardly from contact 19 throughfour holes in contact arm 12, these holes being of larger diameter thanthe studs and being internally threaded. An externally threaded bushing21 is threadably arranged within each of the four holes in contact arm12 and surrounds the stud 20 passing through that hole. Above eachbushing, a nut 22 is threaded on to each of studs 20, and it is theengagement between the nuts 22 and bushings 21 which support contact 19.By rotating bushings 21, the lower ends of which engage contact 19, thecontact can be adjusted toward and away from contact arm 12.

Contact arm 12 is formed with a generally rectangular hole 23 (see FIG.2) through which a leaf spring 24 passes in a downward and forwarddirection, the rearward end of the spring being fixed to the upper faceof arm 12 by screws 25. Spring 24 applies a downward pressure to themovable secondary arcing contact 26. The latter is arranged within acutout in the front endof main contact 19, the rear edge of the cutoutbeing indicated at 27 in FIG. 1.

Mounted on the upper face of contact arm 12, at its end, is a finger 31having an elongated triangular shape when viewed from above, andupturned side edges. A threaded stud 30 projects upwardly from contactarm 12 through a hole in finger 31, this hole being of larger diameterthan the stud and being internally threaded. An externally threadedbushing 32 is threadably arranged within the hole in finger 31 andsurrounds stud 30. Above bushing 32 a nut 33 is threaded on to stud 30.To the rear of stud 30, a screw 34 passes through an elongated hole infinger 31 and is threaded into contact arm 12. In the region of the holeaccommodating screw 34, finger 31 has a downwardly bellied portion 35engaging the upper surface of contact arm 12. It will be appreciated,therefore, that by rotating bushing 32, the lower end of which engagescontact arm 12, the position of finger 31 with respect to arm 12 can beadjusted.

Integral with the free end of finger 31 is the movable primary arcingcontact 36. This contact is in the form of a blade having an attenuatedlower edge 37 which merges into an upwardly and outwardly extending edge38;

Base 10 carries a block 42 (FIG. 1) to which the stationary main contact43 of the switch is secured by fastening means 44. A post 45 is alsomounted on base 10, by fastening means 46, in front of block 42. A fin47 projects rearwardly from post 45 and supports the stationarysecondary arcing contact 48 (FIG. 1).

A pair of arms 51 (FIGS. 1 and 3) flank post 45, these arms carrying attheir upper ends the stationary primary arcing contacts, which accordingto the present invention are a pair of rollers 52. Rollers 52 have acylindrical body portion and a tapered nose, giving them a bulletlikeshape. The manner in which each roller 52 is mounted on its respectivearm 51 is best shown in FIG. 4. A pin 53 projects forwardly from arm 51and has a reduced diameter region 54 between its ends. Hollow roller 52fits over pin 53, for rotation with respect to the pin, and has anannular recess 55 in its inner surface aligned with the reduced diameterportion 54 of pin 53. An elliptically shaped spring clip 56 is arrangedbetween pin 53 and roller 52, the clip portions crossing the minor axisof the clip being accommodated by portion 54, and the clip portionscrossing the major axis of the clip being accommodated by recess 55. Inthis way, clip 56 prevents any substantial relative axial movementbetween pin 53 and roller 52 without preventing relative rotationbetween the two.

Near its upper end, post 45 has a hole through which a pin 60 extends,this pin having an enlarged head 61 at one end and a second enlargedhead 62 threaded on to its other end. Pin 60 also passes loosely throughholes in arms 51. Between each head and its respective arm 51 is acompression spring 63 surrounding pin 60. Springs 63 constantly urgearms 51, and hence rollers 52, toward each other thereby providing goodcontact pressure between contact blade 36 and rollers 52 when thecontact blade is between the rollers.

Spaced below pin 60, post 45 has another hole 64 through which a pin 65extends, this pin having an enlarged head 66 at one end and a secondenlarged head 67 threaded on to its other end. Pin 65 also passesloosely through holes 68 in arms 51. Between each head and itsrespective arm 51 is a compression spring 69 surrounding pin 65. Theregion of each arm 51 surrounding hole 68 has an inwardly directedspherical bulge 70 which seats slidably against a spherical depressionin each face of post 45, in the region surrounding hole 64. Bulges 70and springs 69 define a resilient pivot connection which allows arms 51to swing away from each other, against the force of springs 63, whencontact blade 36 enters between rollers 52 and allows springs 63 toswing arms 51 toward each other when contact blade 36 is removed.

The broken lines in FIG. 1 illustrate the open position of the switchcontact arrangement. When shaft 11 rotates in clockwise direction inFIG. 1, the switch is brought to its closed position shown in solidlines. During movement, from open to closed position, movable primaryarcing contact 36 first engages stationary primary arcing contacts 52.Thereafter, movable secondary arcing contact 26 engages stationarysecondary arcing contact 48, following which movable main contact 19engages stationary main contact 43.

When contact blade 36 first meets rollers 52, as shown in FIG. 4, thereis no possibility of contact bounce since the blade smoothly entersbetween the rollers, this movement being aided by the attenuated edge 37and the cylindrical shape of the rollers. Furthermore, rollers 52 rotateabout their axes, which are parallel to each other and substantiallyperpendicular to the direction of blade movement, as blade 36 movesdownwardly between them. Consequently, there is little frictional dragon the moving contact blade despite the fact that springs 63 and 69create a large contact pressure between the blade and the rollers. Thiscontact pressure is, by the way, increased as a result of the force ofattraction between arms 51, resulting from the magnetic fieldsengendered by electric current flowing in the same direction throughboth arms. An additional advantage of this arrangement is that due torotation of rollers 52, the total contact surfaces of these rollerswhich engage blade 36 are quite large, thereby considerably increasingthe useful life of these contacts.

When shaft 1] rotates in a counterclockwise direction to open theswitch, main contacts 19 and 43 break first, followed by secondaryarcing contacts 26 and 48, after which primary arcing contacts 36 and 52separate. Upon separation, as indicated in FIG. 5, the are 73 drawnbetween the contacts tends to move toward the right in FIG. 5, due tothe magnetic field associated with the current flowing through the arc.Thus, the

- arc runs out along edge 38 and the tapered nose of one or both rollers52. Since edge 38 and the tapered noses diverge in the direction of arcmovement, the length of the arc increases rapidly which of course helpsto extinguish it.

It should be mentioned that all conductors associated with the variouscontacts have been omitted for clarity of illustration. In addition,although the blade and roller contact arrangement has been described inthe present example in connection with primary arcing contacts, thisarrangement can be used with any switch contacts. Furthermore while inthe present illustration the blade contact is the movable contact andthe rollers the stationary contact, obviously this arrangement can bereversed.

The invention has been shown and described in preferred form only, andby way of example, and many variations may be made in the inventionwhich will still be comprised within its spirit. It is understood,therefore, that the invention is not limited to any specific form orembodiment except insofar as such limitations are included in theappended claims.

What is claimed is:

1. An electrical switch including a movable contact and a stationarycontact, one of said contacts including a bladelike member, the other ofsaid contacts including a pair of side-byside rollers between which saidbladelike member is adapted to move when the switch closes, each of saidrollers being generally bullet shaped and having a tapered end, the aredrawn between said movable and stationary contacts moving toward thetips of said tapered ends when the switch opens, resilient means urgingsaid rollers toward each other to provide contact pressure between saidrollers and said bladelike member when the latter is between saidrollers, said rollers being rotatable about parallel axes which aresubstantially perpendicular to the direction of movement of saidbladelike member as it moves between said rollers, whereby when theswitch closes said rollers are rotated as said bladelike member movesbetween them thereby reducing frictional drag between said movable andstationary contacts despite the contact pressure between them.

2. An electrical switch as defined in claim 1 wherein said bladelikemember has an edge facing said rollers when the switch is open, at leasta portion of said edge being arranged at an acute angle to the axes ofrotation of said rollers so that said edge diverges from the taperedends of said rollers, whereby the are drawn between said movable andstationary contacts when the switch opens lengthens as it moves towardthe tips of said rollers and bladelike member.

3. An electrical switch including a movable contact and a stationarycontact, one of said contacts including a bladelike member, the other ofsaid contacts including a pair of side-byside rollers between which saidbladelike member is adapted to move when the switch closes, resilientmeans urging said rollers toward each other to provide contact pressurebetween said rollers and said bladelike member when the latter isbetween said rollers, said rollers being rotatable about parallel axeswhich are substantially perpendicular to the direction of movement ofsaid bladelike member as it moves between said rollers, one of saidcontacts including a pair of arms, each arm carrying one of saidrollers, said arms and hence said rollers being movable away from eachother against the force of said resilient means, the latter constantlyurging said arms and hence said rollers toward each other, a postbetween said arms, a rounded protrusion on each arm spaced from itsrespective rollers, said protrusion engaging said post, whereby each ofsaid arms is pivotable about the point of engagement between itsprotrusion and said post, and additional resilient means urging saidprotrusions against said post.

4. An electrical switch as defined in claim 3 including depressions insaid post within which said protrusions are slidably accommodated.

5. An electrical switch as defined in claim 3 including a hole in eachof said arms, said hole extending through said protrusion, pin meansextending laterally in opposite directions from said post and passingloosely through said holes, and enlargements on the free ends of saidpin means spaced from said arms, and wherein said additional resilientmeans includes a compression spring surrounding said pin means betweeneach of said enlargements and the one of said arms closer to it.

6. An electrical switch as defined in claim 3 including a hole in eachof said arms between its protrusions and its roller, pin means extendinglaterally in opposite directions from said post and passing slidablythrough said holes, and enlargements on the free ends of said pin meansspaced from said arms, and wherein said resilient means includes acompression spring surrounding said pin means between each of saidenlargements and the one of said arms closer to it.

7. An electrical switch as defined in claim 6 including an additionalhole in each of said arms, said additional hole extend-

1. An electrical switch including a movable contact and a stationarycontact, one of said contacts including a bladelike member, the other ofsaid contacts including a pair of side-byside rollers between which saidbladelike member is adapted to move when the switch closes, each of saidrollers being generally bullet shaped and having a tapered end, the arcdrawn between said movable and stationary contacts moving toward thetips of said tapered ends when the switch opens, resilient means urgingsaid rollers toward each other to provide contact pressure between saidrollers and said bladelike member when the latter is between saidrollers, said rollers being rotatable about parallel axes which aresubstantially perpendicular to the direction of movement of saidbladelike member as it moves between said rollers, whereby when theswitch closes said rollers are rotated as said bladelike member movesbetween them thereby reducing frictional drag between said movable andstationary contacts despite the contact pressure between them.
 2. Anelectrical switch as defined in claim 1 wherein said bladelike memberhas an edge facing said rollers when the switch is open, at least aportion of said edge being arranged at an acute angle to the axes ofrotation of said rollers so that said edge diverges from the taperedends of said rollers, whereby the arc drawn between said movable andstationary contacts when the switch opens lengthens as it moves towardthe tips of said rollers and bladelike member.
 3. An electrical switchincluding a movable contact and a stationary contact, one of saidcontacts including a bladelike member, the other of said contactsincluding a pair of side-by-side rollers between which said bladelikemember is adapted to move when the switch closes, resilient means urgingsaid rollers toward each other to provide contact pressure between saidrollers and said bladelike member when the latter is between saidrollers, said rollers being rotatable about parallel axes which aresubstantially perpendicular to the direction of movement of saidbladelike member as it moves between said rollers, one of said contactsincluding a pair of arms, each arm carrying one of said rollers, saidarms and hence said rollers being movable away from each other againstthe force of said resilient means, the latter constantly urging saidarms and hence said rollers toward each other, a post between said arms,a rounded protrusion on each arm spaced from its respective rollers,said protrusion engaging said post, whereby each of said arms ispivotable about the point of engagement between its protrusion and saidpost, and additional resilient means urging said protrusions againstsaid post.
 4. An electrical switch as defined in claim 3 includingdepressions in said post within which said protrusions are slidablyaccommodated.
 5. An electrical switch as defined in claim 3 including ahole in each of said arms, said hole extending through said protrusion,pin means extending laterally in opposite directions from said post andpassing loosely through said holes, and enlargements on the free ends ofsaid pin means spaced from said arms, and wherein said additionalresilient means includes a compression spring surrounding said pin meansbetween each of said enlargements and the one of said arms closer to it.6. An electrical switch as defined in claim 3 including a hole in eachof said arms between its protrusions and its roller, pin means extendinglaterally in opposite directions from said post and passing slidablythrough said holes, and enlargements on the free ends of said pin meansspaced from said arms, and wherein said resilient means includes acompression spring surrounding said pin means between each of saidenlargements and the one of said arms closer to it.
 7. An electricalswitch as defined in claim 6 including an additional hole in each ofsaid arms, said additional hole extending through said protrusion,additional pin means extending laterally in opposite directions fromsaid post and passing loosely through said additional holes, andadditional enlargements on the free ends of said additional pin meansspaced from said arms, and wherein said additional resilient meansincludes a compression spring surrounding said additional pin meansbetween each of said additional enlargements and the one of said armscloser to it.